Electrically-heated soldering-iron.



B. F. GARDNER. ELECTRICALLYHEATED SOLDERING IRON.

APPLICATION FILED JAN.19. 1916.

Patented Sept. Y17, 1918.

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' UNITED sra'ins PATENT onnroa.

BENJAMIN FULTON GARDNER, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TOSEYMOUR STEDMAN, OF CHICAGO, ILLINOIS.

ELECTRICALLY-HEAIED SOLDERING-IRON.

Application filed January 19, 1916. Serial No. 72,959.

To @ZZ whom t may concern.'

Be it known that I, BENJAMIN FULTON GRDNER, a citizen of the UnitedStates, residing at Chicago, in the county of Cook and State ofIllinois, have invented a new and useful Electrically-Heated SolderinIron, of which the following is a speci cation.

My invention relates to improvements in electric heating devices. Moreparticularly the present invention is concerned with the construction ofthe resistor or heating ele ments per se. Theobject of the invention isto provide an improved element ofa com pound nature, embodying twoconductors connected in series, the one having a positive temperaturecoeliicient and the other a negative temperature coeiicient, whereby anaccurate automatic regulation of the heat developed is obtained. theinvention is to provide such a device in a convenient form capable ofbeing readily incorporated in the structure of a heating device suchk asan electric soldering iron.

Other objects and advantages of the invention will appear from thefollowing detailed description of a soldering iron embodying theinvention. In this description reference will,` be had to theaccompanying drawings, in which- Figure 1 is a longitudinal sectionalView of a soldering iron showing my improved heater mounted therein;Fig. 2 is an enlarged longitudinal section through the com-4 poundheating element per se and Fig. 3 is a section on the line 3 of Fig. 2.

The soldering iron shown comprises a tubular handle ysection 10 having agrip pori .tion 11 on its outer end and attached at its other end to anopen-endedcylindrical metallic she-ll 12. A sleeve 13 of mica or otherheat-resisting insulating material lines the shell 12, and within thisliner the heating element. proper is housed. As shown in Fig. 2, thiselement is generally cylindrical in form, comprising an upper section 14and a lower section 15, of the same external diameter and each having acentral aperture through which passes a tie-rod 16 'for binding thesections together. At the upper end the tie-rod is threaded into ashouldered disk 17 which seats upon the upper end of the metalliclannular end-plates 18 of the section 14, and at the lowerend a nut 19 isscrewed upon the rod and bears against an A further object of insulatingwasher 20, the two sections being thus locked together end to end.

The section 14 is preferably constructed of some suitable.heat-resisting high-resistance conducting material having a negativetemperature coefficient, such for instance as carbon or .any of the wellknown refractory earth compositions having the necessary properties.This material is formed into a centrally bored cylinder as shown, cappedby the end plates 18, and preferably having an insulating tube 21 in itsbore. 'Ihe section 15 is preferably formed as a spool of wire such asiron or iron alloy7 having a positive temperature coelicient, the innerend of the wire being grounded to one of a pair of metallic end platesQ2, which bears against and contacts with the plate 18 of the section14, while lthe outer end is left free for the attachment of one ofthecurrent-supplying wires. As shown in Fig. 2, the wire is preferablywound upon the spool with alternate layers of insulating material suchas mica, and with a hollow core registering with the tube 21. Thecomplete heating element is mounted within the shell 12 as shown in Fig.1,` the section 14 being at the 'outer end, and a duplex cable Q3 is ledin through the'hollow handle 10 to supply current to the heater, oneterminal of the cable being attached to the-outer end of the spoolwinding and the other terminal to the inner end of the rod 16. Asoldering iron tip 24 is Specification of Letters latent.` PatentedSept. 17, 1918.

secured in the open outer end of the shell `Vanda mica disk 25 isinterposed between its base and the face of the disk 17.

The operation of my device is as follows:

Assuming that the heating element is cold, the cable Q3 will beconnected with a source of electrical energy of the desired potential,and the current will then How through the length of iron wire upon thespool 15. to end plate 22 from the inner end of this wire, thence bydirect contact to the end plate 18 of the section 14, through the lengthof the latter to the yupper end plate 18 and disk 17, and down'thetie-rod 16, thence back to the 'cable 23. lVhen the heating device iscold the wire upon the spool 15 will have. a relatively low resistance,while the section 14 will have a relatively high resistance. As the twosections become heated the resistance of the spool becomes greater inproportion to its positive temperature coetiicient` while the resistanceof the tubular resistor 14 grows less in proportion to its negativetemperature coeiicient. Each of the sections therefore acts as agovernor, controller or counterbalance for the other, causing the deviceas a whole to heat up quickly to the desired temperature, drawing asubstantially constant current during the entire heating-up period, andthen automatically maintaining this current iiow and temperaturethereafter. A further important advantage of the construction lies inthe fact that small variations in the impressed electro-motive force donot effect more than proportionate variations in the current drawn orthe temperature developed. Thus commercial service lines in variouslocalities may range from 110 to 120 volts for instance. The heater maybe properly designed for ll volts and the variation of 5 volts on eitherside of this standard will have no noticeable effect, the positivetemperature coeiicient of the spool preventing any large increase incurrent which the negative coefficient of the tubular section would tendto cause with increased voltage, and likewise preventing the great dropof current which a small drop in volt-- age will eiect in the tubularsection. Ordinarily the section 14 will be designed to develop aconsiderably greater quantity of heat than the spool l5, the principalfunction of the latter being that of a regulator and its heating eiectbeing a secondary reinforcement of the eiiect ,of the primary heater la.

In the assembly shown in Fig. l the heat developed by the heatingelement will reach the tip Q4 by the direct contact of the base of thelatter with the heater, and also by conduction from the shell l2. Thearrangement here shown is simple and durable and therefore peculiarlyadapted to the demands of ordinary shop conditions.

lVhile I have shown and described in considerable detail one specificembodiment of my heating element and of a device in which l the same isincorporated, it is to be understood that this showing and descriptionis illustrative only and for the purpose of making my invention moreclear and I do '2. The combination with a tubular heating element ofresistance material having a negative temperature coefiicient, a hollowspool of wire in series therewith and abutting the same, and having apositive temperature coeiiicient, and a tie rod extending through theregistering bores of the two members and serving as a conductor forcarelement.

3. The combination with a shell of a tip to be heated secured in theouter end of the said shell, a cylindrical section of resistancematerial having a negative temperature coeticient abutting the said tip,and a coil of wire in series with the said section, abutting theopposite end of the same, and having a positive temperature coefficient.

4. The combination with a shell of a tip to be heated secured in theouter end of the said shell, a t-ubular section of resistance materialhaving a negative temperature coeicient abutting the said tip, a hollowspool of wire arranged in series with the said section and abutting theopposite end ot the same, and a tie rod extending through theregistering bores of the two members and having electrical connectionwith the tip end of the said section.

BENJAMIN FULTON GARDNER.

In presence o A. C. FISCHER, C. C. Ranma.

rying current from the outer end of the said v

